When the French go to the polls today for their first stab at choosing a new president, they may also tilt the balance of power in Europe in the midst of the EU's worst crisis.

The expected triumph for François Hollande will do little to resolve Europe's long-running agony of debt and decline. But it is likely to realign the power politics in the EU. "This election will determine the future of Europe," said a senior social democratic MEP in Brussels.

For Angela Merkel, the German chancellor, who has struck up a close, if awkward, alliance with Nicolas Sarkozy through more than two years of single-currency turbulence, today's election is more important than many of her domestic campaigns, Der Spiegel said last week. "For Merkel, this is an election like no other, and one that is even more important to her than many German state elections. Whoever wins in France will help drive European policy by her side. If the victor proves to be Hollande, things could become uncomfortable for her, both in Brussels and at home in Berlin."

The Merkel camp has been praying for a Sarkozy comeback. In an act of seeming desperation that outraged many in Brussels, the Merkel government joined Sarkozy last week in a joint letter demanding curbs on freedom of travel in the EU's Schengen area, a campaign pledge for the French incumbent.

But Berlin is also resigned to a new French Socialist regime and has been putting out feelers to the Hollande camp. One of Merkel's aides, Nikolaus Meyer-Landrut, is a committed francophile, previously on the staff of ex-president Valéry Giscard d'Estaing and married to a Frenchwoman.

The Franco-German alliance at the heart of Europe is no longer enough to run an EU of 27 countries, but remains a necessary factor. The unlikely "Merkozy" tandem, generated by crisis, has managed to alienate many other EU leaders and the European commission by their summary policymaking.

The alliance has been useful for Merkel, supplying cover for German-scripted policy on the euro, while Sarkozy's second-fiddle status in the relationship has been humiliating for France. It is here that Hollande is planning to challenge Merkel most fundamentally – on the policies and strategies that have entrenched German fiscal rigour and austerity as the eurozone's answer to the crisis.

That means seeking to reform the role of the European Central Bank and discussing Merkel's punitive fiscal pact, reluctantly agreed by 25 EU leaders in March and now being ratified. Hollande says that a France under a new political majority in June will not ratify the existing pact. Merkel, by contrast, is racing to get the German Bundestag to endorse the pact by next month.

Just before campaigning closed in France on Friday, Hollande threw down another gauntlet to the Germans and the ECB. The Frankfurt central bank, he said, should help fix the euro crisis by lending directly to eurozone governments rather than supplying cheap credit to banks.

This is barred by ECB statutes and is anathema to the German political mainstream, the Merkel camp as well as Hollande's allies the Social Democrats, as it is seen as an assault on sacrosanct ECB independence. "Germany is hostile," Hollande admitted last week.

The Franco-German battle over the role of the ECB in running the single currency is as old as the euro itself, with Berlin insisting on a restrictive role guarding monetary stability, while the French argue for an interventionist role priming the eurozone economy.

In the 90s, when the rules were being written, Germany's stability pact became France's stability and growth pact, reflecting the split. But if the French won the extra words, they have yet to win the real battle over policy and power.

The Germans may feel that they have already set the terms and entrenched the instruments for trying to tackle the crisis. But in the politics of the campaign to save the euro, a backlash is gathering against Berlin's austerity medicine – in Spain, in Italy, in the International Monetary Fund, in the European commission. An Hollande victory will reinforce this trend. "Everything we are doing now is aimed towards helping growth," said the Italian prime minister, Mario Monti, on Wednesday, announcing a dilution of austerity measures. Hollande adds that he will gain allies in Spain and the Netherlands, both having to contend with massive spending cuts, and that this will strengthen him in his challenge to Merkel.

"As for Germany, it understands that it can't remain an island of prosperity in the middle of an ocean of recession," he told the French newspaper, Les Echos. "Can you imagine for a moment that Germany would want to direct Europe alone and isolate France?"

Despite the policy differences, Hollande stresses that he wants a strong relationship with Merkel. The chances of that look good.

The Franco-German partnerships of the past 30 years – Schröder-Chirac, Kohl-Mitterrand, Schmidt-Giscard – have been of the centre-right and centre-left. Temperamentally, however, Merkel and Hollande have more in common than the German has with Sarkozy. Both are cautious, centrist policy wonks, risk-averse, unflamboyant. Funny and mischievous in private, dull in public.

It remains to be seen how much is campaign rhetoric and how much compromise can be reached if Hollande moves into the Elysée Palace. He told Les Echos there was more at stake than France's fortunes.

"Change in France will allow Europe to shift direction. The [second round] 6 May date is also a decisive deadline for the future of our continent."